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[209.132.180.67]) by mx.google.com with ESMTP id d3si2123437pfa.234.2019.06.07.08.44.45; Fri, 07 Jun 2019 08:45:01 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=A73obezV; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730152AbfFGPkv (ORCPT + 99 others); Fri, 7 Jun 2019 11:40:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:50202 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730135AbfFGPkr (ORCPT ); Fri, 7 Jun 2019 11:40:47 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F0FC4212F5; Fri, 7 Jun 2019 15:40:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559922047; bh=s5XUr4oAMYMkO/L1yXi+KcIP++cyMJwnAPtD+Pi+5qY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=A73obezVzLQOzOnBO1YFSvuZlyTcGahv3TulGmPqgDJT7Y0MdHfGqrSbWl+RVm4kT yuxmFQrEjrkhpOdoy/t3Mn0JD/cryH7exKxe3fQ7eESgMWVbjao/FrTAE9KrXJBlqw 6A5Chut4y59hJMZuKUMnQDVE+YP4/E5R002/pmL0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Beulich , Konrad Rzeszutek Wilk , Prarit Bhargava , Juergen Gross , Ben Hutchings Subject: [PATCH 4.14 18/69] xen/pciback: Dont disable PCI_COMMAND on PCI device reset. Date: Fri, 7 Jun 2019 17:38:59 +0200 Message-Id: <20190607153850.560174860@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190607153848.271562617@linuxfoundation.org> References: <20190607153848.271562617@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Konrad Rzeszutek Wilk commit 7681f31ec9cdacab4fd10570be924f2cef6669ba upstream. There is no need for this at all. Worst it means that if the guest tries to write to BARs it could lead (on certain platforms) to PCI SERR errors. Please note that with af6fc858a35b90e89ea7a7ee58e66628c55c776b "xen-pciback: limit guest control of command register" a guest is still allowed to enable those control bits (safely), but is not allowed to disable them and that therefore a well behaved frontend which enables things before using them will still function correctly. This is done via an write to the configuration register 0x4 which triggers on the backend side: command_write \- pci_enable_device \- pci_enable_device_flags \- do_pci_enable_device \- pcibios_enable_device \-pci_enable_resourcess [which enables the PCI_COMMAND_MEMORY|PCI_COMMAND_IO] However guests (and drivers) which don't do this could cause problems, including the security issues which XSA-120 sought to address. Reported-by: Jan Beulich Signed-off-by: Konrad Rzeszutek Wilk Reviewed-by: Prarit Bhargava Signed-off-by: Juergen Gross Cc: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- drivers/xen/xen-pciback/pciback_ops.c | 2 -- 1 file changed, 2 deletions(-) --- a/drivers/xen/xen-pciback/pciback_ops.c +++ b/drivers/xen/xen-pciback/pciback_ops.c @@ -127,8 +127,6 @@ void xen_pcibk_reset_device(struct pci_d if (pci_is_enabled(dev)) pci_disable_device(dev); - pci_write_config_word(dev, PCI_COMMAND, 0); - dev->is_busmaster = 0; } else { pci_read_config_word(dev, PCI_COMMAND, &cmd);